P P & P P P ?

Before the NIMT railway was finished in 1908, nearly every hectare of land in the Waimarino was covered in native forest that had taken about -800 tonne of CO₂ per hectare from the atmosphere, storing 600 tonne of it in living wood and 200 tonne in humus.

Timber millers removed about 300 tonne of CO2 per hectare, and about 200 tonne of CO₂ is probably still stored in house timbers, while the remainder of the timber has been burnt and turned back to +100 tonne of CO₂.

Market gardeners burnt the remaining wood trash, releasing another +300 tonne of CO₂.

Continually cultivating the soil for vegetables decomposed most of the humus, releasing another +150 tonne of CO₂.

Sowing old market gardens in pasture removed about -50 tonne of CO₂ per hectare from the atmosphere, creating about 14 tonne of trapped carbon per hectare.

Therefore every hectare of Waimarino rainforest converted to market garden, then pasture, has put about +500 tonne of CO₂ back into the atmosphere.

When 3 head of cattle are grazed on this hectare of pasture, they convert about 400 grams of trapped pasture carbon into 530 grams of methane (CH₄) each day, or about 190 kg per year.

About 10% of this methane is lost each year, so in 10 years our 3 head of cattle have converted about 2.8 tonne of atmospheric CO₂ into 1 tonne of CH₄ in the air, and that remains as a steady amount.

But one tonne of CH₄ in the atmosphere traps 85 times as much heat as CO₂, so 3 head of cattle on one hectare are constantly removing about -2.8 tonne of CO₂ and keeping the heating equivalent of an extra +85 tonne of CO₂ to the atmosphere. Or adding an extra 29 tonne CO₂ equivalent per beast.

Thus every hectare of Waimarino rain forest converted to agriculture, then to ruminant farming, has added the greenhouse equivalent of about 585 tonne of CO₂ to the atmosphere, or about 195 ton of CO₂ per cattle beast.

New Zealand ruminants (cows, steers, bulls , sheep, deer, goats, pigs) are keeping the CH₄ equivalent produced by about 12 million cattle beasts, or about an extra 350 million tonne of CO₂ eqiv, in the atmosphere.

If 4 million hectares of New Zealand's ruminant pasture land was replanted as native rain forest, then about 2,300 million tonne of CO₂ eqiv would eventually be removed from the atmosphere.

But every year, unfortunately, the world population increases by about another 50 million people, and another 4 million hectares of forest worldwide is converted to farmland to feed them, about half of it for ruminant farming, and about 4 times as much CH₄ is leaking from natural gas pipe lines. So the Pipiriki Pineapple & Pawpaw Production Partnership might be a better investment than Turoa skifield.

John Archer            
November 2022